The disclosure relates generally to rotary electric machines, and more particularly, to monitoring of stator coil coolant flow reduction.
Rotary electric machines such as an electrical generator include a rotor within a stator, the latter of which includes a number of conductor sections having slots therein into which stator coils are placed. During operation or, specifically, delivering output power, the generator creates heat such that direct liquid cooling of the stator coils is required to prevent overheating. A cooling liquid, e.g., de-ionized water with anti-freeze, is passed through passages in the stator coils. One challenge relative to the cooling process is that coolant flow is subject to flow reduction up to and including complete blockage, either of which can cause a forced outage of the electric generator. A portion of the stator coils can have a coolant flow reduction due to, for example, debris, loose solids, swelling of existing material, or gas locking. During coolant flow reduction, a reduced liquid flow causes a rise in the slot (winding/coil) temperature and subsequently the coolant outlet temperature, which may result in coil failure.
In order to prevent forced outage due to flow reduction, stator coils are protected from overheating by monitoring coolant outlet temperature. This monitoring, however, is limited in its efficacy due to its limited scope. Another challenge in performing the monitoring is that data received through the sensors may have quality issues such as erratic behavior of the sensor, noise in the sensor, improper calibration, connection/wiring issues, etc. Consequently, the ability to validate the sensors such that coolant flow reduction can be diagnosed over a long duration is a concern.